Person: GÜLÇEBİ İDRİZ OĞLU, MEDİNE
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GÜLÇEBİ İDRİZ OĞLU
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Publication Open Access The pathways connecting the hippocampal formation, the thalamic reuniens nucleus and the thalamic reticular nucleus in the rat(WILEY, 2008-03) ONAT, FİLİZ; Cavdar, Safiye; Onat, Filiz Y.; Cakmak, Yusuf Oezguer; Yananli, Hasan R.; Gulcebi, Medine; Aker, RezzanMost dorsal thalamic nuclei send axons to specific areas of the neocortex and to specific sectors of the thalamic reticular nucleus; the neocortex then sends reciprocal connections back to the same thalamic nucleus, directly as well indirectly through a relay in the thalamic reticular nucleus. This can be regarded as a 'canonical' circuit of the sensory thalamus. For the pathways that link the thalamus and the hippocampal formation, only a few comparable connections have been described. The reuniens nucleus of the thalamus sends some of its major cortical efferents to the hippocampal formation. The present study shows that cells of the hippocampal formation as well as cells in the reuniens nucleus are retrogradely labelled following injections of horseradish peroxidase or fluoro-gold into the rostral part of the thalamic reticular nucleus in the rat. Within the hippocampal formation, labelled neurons were localized in the subiculum, predominantly on the ipsilateral side, with fewer neurons labelled contralaterally. Labelled neurons were seen in the hippocampal formation and nucleus reuniens only after injections made in the rostral thalamic reticular nucleus (1.6-1.8 mm caudal to bregma). In addition, the present study confirmed the presence of afferent connections to the rostral thalamic reticular nucleus from cortical (cingulate, orbital and infralimbic, retrosplenial and frontal), midline thalamic (paraventricular, anteromedial, centromedial and mediodorsal thalamic nuclei) and brainstem structures (substantia nigra pars reticularis, ventral tegmental area, periaqueductal grey, superior vestibular and pontine reticular nuclei). These results demonstrate a potential for the thalamo-hippocampal circuitry to influence the functional roles of the thalamic reticular nucleus, and show that thalamo-hippocampal connections resemble the circuitry that links the sensory thalamus and neocortex.Publication Open Access The role of the substantia nigra pars reticulata in kindling resistance in rats with genetic absence epilepsy(WILEY, 2015-11) ONAT, FİLİZ; Akman, Ozlem; Gulcebi, Medine I.; Carcak, Nihan; Ozatman, Sema Ketenci; Eryigit, Tugba; Moshe, Solomon L.; Galanopoulou, Aristea S.; Onat, Filiz YilmazObjectiveGenetic Absence Epilepsy Rats from Strasbourg (GAERS) show a resistance to secondary generalization of focal limbic seizures evoked by kindling. The substantia nigra pars reticulata (SNR) is involved in the propagation and modulation of seizures in kindling. We first examined the role of the SNRanterior and SNRposterior subregions in the resistance to the development of kindling in GAERS. Subsequently, to determine whether kindling resistance relates to differential sensitivity of -aminobutyric acid -aminobutyric acid (GABA)ergic or dopaminergic SNR neurons to kindling, we studied the effects of kindling-inducing stimulations on parvalbumin (PRV; GABAergic neuron marker) or tyrosine hydroxylase (TH; dopaminergic neuron marker) immunoreactivity (ir), respectively, in GAERS and in nonepileptic control (NEC) Wistar rats that lack kindling resistance. MethodsAdult male GAERS were implanted with a stimulation electrode in the amygdala, and bilateral injection cannulas for lidocaine or saline injection (30 min before each kindling stimulation until the animals reached three stage 5 seizures or the 22 stimulations) into the SNRanterior or SNRposterior. In another experiment, PRV-ir in SNRanterior and SNRposterior and TH-ir in SNRposterior only were densitometrically compared in GAERS-SHAM, NEC-SHAM GAERS-STIM, and NEC-STIM animals (6 kindling stimulations). ResultsBilateral SNRposterior infusions of lidocaine eliminated the kindling resistance and resulted in stage 5 generalized motor seizures in all kindled rats. Bilateral lidocaine infusions in the SNRanterior failed to alter the kindling resistance in GAERS. PRV-ir in the SNRposterior was unaltered in GAERS-STIM but increased in NEC-STIM group. Cellular TH-ir in the SNRposterior significantly increased by kindling stimulations in both NEC-STIM and GAERS-STIM groups. SignificanceThe kindling resistance in GAERS is mediated by the SNRposterior in a lidocaine-sensitive manner. The insensitivity to kindling stimulation of PRV-ir in SNRposterior of GAERS but not NEC rats, implicate GABAergic SNRposterior neurons in kindling resistance. In contrast, the observed stimulation-specific increase in TH-ir in the SNRposterior is unrelated to kindling resistance.Publication Metadata only Topographical connections of the substantia nigra pars reticulata to higher-order thalamic nuclei in the rat(PERGAMON-ELSEVIER SCIENCE LTD, 2012) ONAT, FİLİZ; Gulcebi, Medine Idrizoglu; Ketenci, Sema; Linke, Rudiger; Hacioglu, Husniye; Yanali, Hasan; Veliskova, Jana; Moshe, Solomon L.; Onata, Filiz; Cavdar, SafiyeThe substantia nigra pars reticulata (SNR) is the ventral subdivision of the substantia nigra and contains mostly GABAergic neurons. The present study explores whether the SNR relates to all dorsal thalamic nuclei equally or just to a particular group of nuclei, such as first or higher-order nuclei. Injections of biotinylated dextran amine (BDA) were made into the SNR of 10 male adult rats. The distribution of anterogradely labelled axon terminals in the thalamic nuclei was documented. The projections of the SNR to the thalamic nuclei were exclusively to some motor higher-order, but not to first-order thalamic relays. There were bilateral projections to the ventromedial (VM), parafascicular (PF), centromedian (CM) and paracentral (PC) nuclei and unilateral projections to the centrolateral (CL), mediodorsal (MD) and thalamic reticular nucleus (Rt). Labelled axon terminals in the thalamic nuclei ranged from numerous to sparse in VM, PF, CM, CL, PC, MD and Rt. Further, injections into the SNR along its rostral-caudal axis showed specific topographical connections with the thalamic nuclei. The rostral SNR injections showed labelled axon terminals of VM, PF, CL, PC, CM, MD and Rt. Caudal SNR injections showed labelling of VM, PF, PC, CM and MD. All injections showed labelled axons and terminals in the zona incerta. The nigrothalamic GABAergic neurons can be regarded as an important system for the regulation of motor activities. The SNR is in a position to influence large areas of the neocortex by modulating some of the motor higher-order thalamic nuclei directly or indirectly via Rt. (C) 2011 Elsevier Inc. All rights reserved.Publication Open Access Evaluation of GAD67 immunoreactivity in the region of substantia nigra pars reticulata in resistance to development of convulsive seizure in genetic absence epilepsy rats(KARE PUBL, 2016) ONAT, FİLİZ; Gulcebi, Medine; Akman, Ozlem; Carcak, Nihan; Karamahmutoglu, Tugba; Onat, FilizOBJECTIVE: Nonconvulsive absence epilepsy and convulsive epilepsy seizures are rarely seen in the same patient. It has been demonstrated that there is a resistance to development of convulsive seizures in genetic absence epilepsy models. The present study investigated glutamic acid decarboxylase (GAD) immunoreactivity in the brain region related to the interaction of these two seizure types, namely substantia nigra pars reticulata (SNR) subregions, SNRantenor and SNRpostenor. METHODS: Nonepileptic adult male Wistar rats and Genetic Absence Epilepsy Rats from Strasbourg (GAERS) were used. Experimental groups of Wistar and GAERS were electrically stimulated for kindling model to induce convulsive epileptic seizures. An electrical stimulation cannula was stereotaxically implanted to the basolateral amygdala and recording electrodes were placed on the cortex. Sagittal sections of SNR were used to evaluate immunohistochemical reaction. Sections were incubated with anti-GAD67 antibody. Densitometric analysis of GAD67 immunoreactive neurons was performed using photographs of stained sections. One-way analysis of variance and post hoc Bonferroni test were used for statistical analysis of the data. RESULTS: There was no difference in GAD67 immunoreactivity of SNR subregions of control Wistar and control GAERS. An increase in GAD67 immunoreactivity was detected in SNRposterior subregion of stimulated Wistar rats, whereas there was a decrease in GAD67 immunoreactivity in SNRposterior of stimulated GAERS. The difference in GAD67 immunoreactivity between these two groups was statistically significant. CONCLUSION: Level of synthetized gamma-aminobutyric acid in SNRposterior subregion plays an important role in the interaction of nonconvulsive absence epilepsy seizures and convulsive epilepsy seizures.